2. XSLT
● XSLT stands for Extensible Stylesheet Language
Transformations
● XSLT is used to transform XML documents into other
kinds of documents--usually, but not necessarily, XHTML
● XSLT uses two input files:
The XML document containing the actual data
The XSL document containing both the “framework” in which
to insert the data, and XSLT commands to do so
3. Simple example
File data.xml:
<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="render.xsl"?>
<message>Howdy!</message>
File render.xsl:
<?xml version="1.0"?>
<xsl:stylesheet version="1.0”
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<!-- one rule, to transform the input root (/) →
<xsl:template match="/">
<html><body>
<h1><xsl:value-of select="message"/></h1>
</body></html>
</xsl:template>
</xsl:stylesheet>
4. The .xsl file
An XSLT document has the .xsl extension
The XSLT document begins with:
<?xml version="1.0"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
Contains one or more templates, such as:
<xsl:template match="/"> ... </xsl:template>
And ends with:
</xsl:stylesheet>
5. xsl:value-of
<xsl:value-of select="XPath expression"/> selects
the contents of an element and adds it to the output stream
The select attribute is required
Notice that xsl:value-of is not a container, hence it needs to
end with a slash
Example (from an earlier slide):
<h1> <xsl:value-of select="message"/> </h1>
6. xsl:for-each
xsl:for-each is a kind of loop statement
The syntax is
<xsl:for-each select="XPath expression">
Text to insert and rules to apply
</xsl:for-each>
Example: to select every book (//book) and make an unordered
list (<ul>) of their titles (title), use:
<ul> <xsl:for-each select="//book">
<li> <xsl:value-of select="title"/> </li> </xsl:for-each> </ul>
7. Filtering output
You can filter (restrict) output by adding a criterion
to the select attribute’s value:
<ul> <xsl:for-each select="//book">
<li>
<xsl:value-of select="title[../author='Terry Pratchett']"/>
</li> </xsl:for-each>
</ul>
This will select book titles by Terry Pratchett
8. Filter details
Here is the filter we just used:
<xsl:value-of select="title[../author='Terry Pratchett']"/>
author is a sibling of title, so from title we have to
go up to its parent, book, then back down to author
This filter requires a quote within a quote, so we need
both single quotes and double quotes
Legal filter operators are:
= != < >
Numbers should be quoted, but apparently don’t have to be
9. xsl:if
xsl:if allows us to include content if a given condition (in the test attribute) is true
Example:
<xsl:for-each select="//book">
<xsl:if test="author='Terry Pratchett'">
<li> <xsl:value-of select="title"/>
</li>
</xsl:if>
</xsl:for-each>
This does work correctly!
10. xsl:choose
The xsl:choose ... xsl:when ... xsl:otherwise
construct is XML’s equivalent of Java’s switch ... case ... default statement
The syntax is:
<xsl:choose>
<xsl:when test="some condition">
... some code ...
</xsl:when> <xsl:otherwise>
... some code ...
</xsl:otherwise>
</xsl:choose>
• xsl:choose is often used within an xsl:for-each loop
11. xsl:sort
You can place an xsl:sort inside an xsl:for-each
The attribute of the sort tells what field to sort on Example:
<ul>
<xsl:for-each select="//book">
<xsl:sort select="author"/>
<li>
<xsl:value-of select="title"/> by <xsl:value-of select="author"/>
</li>
</xsl:for-each>
</ul>
This example creates a list of titles and authors, sorted by author
12. xsl:text
<xsl:text>...</xsl:text>
XSL isn’t very careful with whitespace in the document
This doesn’t matter much for HTML, which collapses all whitespace anyway
(though the HTML source may look ugly)
<xsl:text> gives you much better control over whitespace; it acts like the <pre>
element in HTML
13. Quick questions
- What are the input files in XSLT?
- Mentions 2 commands in XSL
- ¿What does the command choose?
14. Applying templates to children
<book>
<title>XML</title>
<author>Gregory Brill</author>
</book>
<xsl:template match="/">
<html> <head></head> <body>
<b><xsl:value-of select="/book/title"/></b>
<xsl:apply-templates select="/book/author"/>
<xsl:apply-templates select="/book/title"/>
</body> </html>
</xsl:template>
<xsl:template match="/book/author">
by <i><xsl:value-of select="."/></i>
</xsl:template>
With this line:
XML by Gregory Brill
Without this line:
XML
15. Calling named templates
You can name a template, then call it, similar to the way you
would call a method in Java
The named template:
<xsl:template name="myTemplateName">
...body of template...
</xsl:template>
A call to the template:
<xsl:call-template name="myTemplateName"/>
Or:
<xsl:call-template name="myTemplateName">
...parameters...
</xsl:call-template>
16. Templates with parameters
Parameters, if present, are included in the content of
xsl:template, but are the only content of xsl:call-template
Example call:
<xsl:call-template name="doOneType">
<xsl:with-param name="header" select="'Lectures'"/>
<xsl:with-param name="nodes" select="//lecture"/> </xsl:call-template>
Example template:
<xsl:template name="doOneType"> <xsl:param name="header"/> <xsl:param name="nodes"/>
...template body...refer to parameters as "$header" and "$nodes" </xsl:template>
Parameters are matched up by name, not by position
Single quotes inside double
quotes make this a string
This parameter is a
typical XPath
expression
17. Thoughts on XSL
XSL is a programming language--and not a particularly simple one
Expect to spend considerable time debugging your XSL
These slides have been an introduction to XSL and XSLT--there’s a lot more of it we haven’t covered
As with any programming, it’s a good idea to start simple and build it up incrementally: “Write a little, test
a little”
This is especially a good idea for XSLT, because you don’t get a lot of
feedback about what went wrong
I use jEdit with the XML plugin
I find it to be a big help, especially with XML syntax
My approach is: write (or change) a line or two, check for syntax errors,
then jump to IE and reload the XML file
